1. Field of the Invention
This invention pertains to an improved method for the preparation of a stable sweetening agent delivery system wherein the sweetening agent is protected by a matrix coating capable of effecting a controlled release of the sweetening agent. The sweetening agent delivery system may be incorporated into chewing gum and confectionery compositions to provide prolonged sweetness. More particularly, this invention pertains to an improved method for the preparation of such sweetening agent delivery systems on commercial scale.
2. Description of the Prior Art
Coatings for sweetening agents (sweeteners) to delay or prolong sweetness, as well as to stabilize sensitive sweetening agents, are well known. Nevertheless, certain sweetening agents, such as Aspartame, are particularly difficult to coat because Aspartame crystals are rod-like, needle-like or dendritic in shape and are particularly difficult to wet. As a result, it is very difficult to coat Aspartame crystals using ordinary mixing and spray coating techniques. To effectively protect Aspartame, a coating must (a) wet and adhere to the crystalline surface, including the needle-like and rod-like tips and other shape variations of the crystal, (b) form a film with a uniform thickness sufficient to provide a barrier against degradative factors such as moisture, pH changes, temperature changes and reactive chemicals, and (c) be flexible enough to conform to crystal surface irregularities without cracking due to mechanical stresses applied during incorporation of the sweetening agent into final products. Attempts to coat Aspartame crystals using mixing and spray techniques to apply simple mixtures of fat and lecithin have resulted in poor wetting and spotty coating of the crystals and hence inadequate protection of the core material against moisture and other degradative factors. Furthermore, many of these coating materials require solvents and water for application, and such solvents and water adversely effect the stability of hydrophilic unstable materials such as Aspartame.
Prior art techniques for coating difficult-to-coat materials such as Aspartame, generally involve spray coating the core material in a fluidized bed or mixing the core material with molten coating material and pulverizing the cooled mixture. Fluidized bed spray coating involves suspending a mass of core material in a stream of air passing through a zone of atomized droplets of the coating material. Spray coating of Aspartame in a fluidized bed system is difficult because Aspartame is a low density material, has a large surface to weight ratio and has poor wetting characteristics. Forming a molten mixture of coating material with the sweetening agent, pulverizing the solidified mixture results in particles which are incompletely coated and which are not adequately protected. On a large commercial scale, coating these difficult-to-coat materials is even more difficult.
U.S. Pat. No. 4,384,004, issued to Cea et al., discloses solid particles of Aspartame encapsulated by a coating material selected from the group consisting of cellulose, cellulose derivatives, arabinogalactin, gum arabic, polyolefins, waxes, vinyl polymers, gelatin, zein, and mixtures thereof. The Aspartame particles are suspended in a stream of air that passes through a zone of atomized liquid droplets of the coating material. More than one coating may be used whereby the inner coating is water-soluble and the outer coating is water-soluble.
U.S. Pat. No. 4,122,195 and U.S. Pat. No. 4,139,939, issued to Bahoshy et al., coat Aspartame by spray drying a mixture of Aspartame and a film forming agent with a material such as gum arabic or the reaction product of a compound containing a polyvalent metallic ion, with an ungelatinized acid-ester of a substituted dicarboxylic acid.
U.S. Pat. No. 4,374,858, issued to Glass et al., discloses a sweetened chewing gum comprising Aspartame having improved sweetness stability wherein the chewing gum piece has Aspartame coated on the gum surface, as opposed to incorporating Aspartame in the chewing gum mix.
U.S. Pat. No. 4,105,801, issued to Degliotti, discloses a confectionery composition comprising a core portion and a shell enveloping the core portion, whereby the shell comprises an intimate mixture of microcrystals of xylitol with a solid fatty substance in a proportion of 0.5 to 15 parts of fatty substance to 100 parts of xylitol by weight. The fatty substance is preferably a mono-, di- or triglyceride having a melting range between 20.degree. C. and 60.degree. C.
U.S. Pat. No. 3,389,000, issued to Toyonaka et al., discloses a spray drying process for preparing granular coated nucleoside-5-phosphates. The coatings may be edible animal and plant fats melting between 40.degree. C.-100.degree. C. such as hydrogenated oils including soybean oil, cottonseed oil, almond oil, castor oil, linseed oil, mustard oil, olive oil, grapefruit seed oil, palm oil, palm kernel oil, rapeseed oil, rice bran oil, and the like, and mixtures of these oils.
U.S. Pat. No. 4,382,924, issued to Berling, discloses liquid oral dosage forms for vitamins or pharmaceutical materials comprising an edible oil, a high potency lipid soluble sweetening agent such as Saccharin and a lipid soluble flavorant. The edible oil may be a polyol fatty acid ester having at least four fatty acid ester groups and each fatty acid having from about 8 to about 22 carbon atoms. The oil, sweetening agent and flavor oil are heated and mixed, then cooled to provide a palatable liquid dosage form.
For a general discussion of spray coating fatty materials onto sweetening agents, and the like, see U.S. Pat. No. 3,949,094 and U.S. Pat. No. 3,976,794, issued to Johnson, and U.S. Pat. No. 3,867,556, issued to Darragh. U.S. Pat. No. 4,293,572, issued to Silva et al., discloses the application of a dispersion of an emulsified fat with a solution of dextrin, Saccharin or a polysaccharide to a food product as a barrier against moisture.
European patent application number 81110320.0, published June 16, 1982, to Ajinomoto-Co., Inc., discloses a stabilized dipeptide-based sweetening composition comprising in percentages by weight (a) from 20% to 60% of solid fat, (b) from 10% to 30% of emulsifier, (c) from 10% to 30% of polysaccharide, and (d) not more than 30% of a dipeptide sweetening agent. The compositions are prepared by spray coating the sweetening agent or by heating and mixing a mixture of sweetening agent and coating material, cooling the mixture, then pulverizing the mixture to obtain powder or granules.
U.S. Pat. No. 4,597,970, issued to Sharma et al., discloses a delivery system wherein a sweetening agent is coated with a mixture of fatty acid or wax, lecithin and monoglyceride. The delivery system protects and controls release of the sweetening agent.
U.S. Pat. No. 4,816,265, issued to Cherukuri et al., discloses a chewing gum composition containing a sweetening agent delivery system which consists essentially of (a) at least one solid natural or artificial high intensity sweetening agent present in an amount from about 0.01% to about 50%, (b) an emulsifying agent present in an amount from about 0.5% to about 20%, and (c) polyvinyl acetate present in an amount from about 40% to about 93% and having a molecular weight range from about 2,000 to about 14,000. The method disclosed for preparing the sweetening agent delivery system is designed for small scale preparations of coated material and is not convenient on a commercial scale.
Thus, numerous methods are known for preparing coated sweetening agents which have varying degrees of effectiveness in protecting, and providing controlled release of, the core material. None of these methods however provides an effective means on commercial scale for coating core materials which are sensitive and have crystalline structures which are difficult to wet and to coat. The present invention provides such a method for preparing a stable sweetening agent delivery system wherein the sweetening agent core material is protected by a matrix coating which is also capable of providing controlled release of the sweetening agent. More particularly, the present invention provides a method for preparing a stable sweetening agent delivery system on commercial scale.